Producing aluminate from alunite.



UNITED STATES PATENT OFFICE.

PAUL R. HERSHMAN, OF CHICAGO, ILLINOIS.

PRODUCING AL'U'MINA'IE FROM ALUNITE.

. 1 191 104 Specification of Letters Patent.

No Drawing.

To all whom it may concern:

Be it known that I, PAUL R. HE'RsHMAN, a citizen of the Empire ofAustria-Hungary, residing in Chicago, county of Cook, State of Illinois,have invented certain new and useful Improvements in Producing Aluminate from Alunite: and I do hereby declare the following to be a full,clear, and exact description of the invention, such as will enableothers skilled in the art to which it v appertains to make and use thesame.

My invention relates to the treatment of alunite and to the recoverytherefrom of free from even traces of silica.

potassium aluminate, and alumina, in an alkali-soluble form.

In the manufacture of potassium com pounds and alumina from alunite, asheretofore practised, the alunite is calcined at temperatures of about700-1200 C. Potassium sulfate and alumina are formed; and the product isthen extracted with water, leaving the alumina as residue, together withthe impurities originally contained in the alunite, such as iron andsilica. I have found that when the alunite is mixed with a suitableamount of oxids from the group of alkaline earths, such as calcium oxid,and heated to temperatures from 1000 C. to preferably 1200 C., (but inno case exceeding 1400 C.) and particuarly when certain fluxes such assodium chlorid are mixed with the charge, or, when the reaction isassisted by superheated steam, a

portion of the alumina contained in the alucombine being one molecule ofalumina to j one molecule of potassium oxid. The potassium aluminatesolutions obtained are In addition, the alumina which has not beenconverted into aluminate is, through this heat ing process, convertedinto an alkali-soluble form. After the completion of the reaction, onlytraces of sulfuric acid or sulfids are found in the product obtained.

Most of thecalcium oxid used is found in its original form, after thecompletion of the reaction, instead of in the form of calcium sulfate,so that it would seem that any calcium sulfate which might be formed asan intermediate product is immediately decomposed, although thedecomposition of Patented July 11, 1916.

Application filed January 18, 1916. Serial No. 72,689.

ture, would not take place at such low temperatures.

When alunite is heated alone, no aluminate is formed below 1000 C., andbut a small percentage above that temperature. The addition of calciumoxid, however, in all cases, is found to increase materially theformation of soluble alumina and aluminate, and under the most favorableconditions all the potassium contained in the raw alunite as sulfategives up its contents of sulfuric acid and combines with such part ofthe alumina as corresponds to the proportion: one molecule K 0 to onemolecule A1 0,. If, now, in addition to the compounds added to cause theconversion of all the potassium oxld contained into potassium aluminate(calcium oxid' and flux), such an amount of alkaline potassium salts, orpotassium sulfate and carbon is added, as is necessary to combine withthe surplus of alumina (2'. 6., that part of the alumina which does notcombine with the potassium oxidfrom the potassium sulfate of thealunite) in the proportion of one molecule of potassium oxid to onemolecule of the surplus alumina, then the alumina contained in-thealunite can be converted into aluminate with substantially quantitativeyields.

It has been mentioned above that the potassium aluminate'solutionobtained by dissolving the potassium aluminate (produced from thepotassium originally contained in the raw alunite) is free of silica.Furthermore, if the Washed residue, consisting of the surplus of aluminaand the impurities, is heated with alkali, the solutions obtained arefound to be practically free from silica, probably because the latterhas, during the heating process, been converted into alkaln insolublecalcium silicate. This is a great advantage, no loss of alkali beingcaused by the combining with alkali-soluble silica.

The invention will be further illustrated by the following specificinstances of its application:

Example 1: 100 parts by weight of finely pulverized crude basic alunite(such as is found in large deposits in Utah) are mixed with 10 parts byweight of salt and 15' parts by weight of calcium oxid and heated inamuiiiefurnaceat'lQOO" C. for two hours. The product obtained istreated, preferably under pressure of 150, to 175 pounds per squareinch, with hot water of a correspond- I ing temperature, although theuse of pressure is not absolutely essential. The potassium aluminateformed is thus brought into solution, and the residue, after being wellwashed with water and freed of potassium aluminate consists ofalkali-soluble alumina and all the impurities, butis substantially freefrom potassium compounds, either water-soluble or water-insoluble. Thealumina is then extracted by a boiling solution of an alkali in amountsufficient to dissolve the alumina, the employment of pressurefacilitating the extraction. and reprecipitated by any of the well-knownmethods, the sodium aluminate solution obtained during the processbeingpractically free of silica.

Example 2: 100 parts by weight of raw alunite are mixed with 15 parts byweight of lime (CaO) parts by weight of potassium sulfate, and15 partsof carbon; this mixture is heated to 1150 C. for half an.

hour in the presence of steam. The product obtained is treated,preferably under pressure of 150 to 175 pounds, with four parts of waterfor each part of potassium aluminate formed during the calcination, andthe alumina and potassium compounds are separated as above. H

Example 3:100 parts by weight of calcined alunite are mixed with 15parts by weight of lime ((12.0) and 50 parts by weight of potassiumcarbonate, and kept at 1150 C. for one hour. The product ob? tained isthen treated with water as per Example 2. i

It will of course be understood that many changes of minor importancecan be made in the invention as described, without departing from itsspirit and scope. F orinstance, instead of potassium icompounds, sodiumsalts may be employed, etc.

I claim':

1. The method of producing potassiumaluminate from alunite, whichcomprises treating the raw aluniteat temperatures not exceeding 1400 C.with an oxid of an' alkaline earth, ,and subsemiently dissolving out thepotassium aluminate from the resulting mass, under pressure;substantially as described.

2. The method of producing potassium aluminate, from alunite, whichcomprises treating the raw alunite at temperatures not exceeding 1400 C.with an oxid of an aklaline earth and with a flux, and subsequentlydissolving out the potassium aluminate from the resulting mass underpressure;-substantially as described.

mass under 3. The method of producing potassium aluminate from alunite,which comprises treating the raw alunite at temperatures not exceeding1400 C. with an oxid of. an alkaline earth and with superheated steam,and

subsequently dissolving out the potassium aluminate from the resultingmass under pressure; substantially as described.

4. The method of producing potassium aluminate from alunite, whichcomprises treating the raw alunite at temperatures not exceeding 1400 C.with an oxid of an alkaline earth, a flux, and superheated steam, andsubsequently dissolving out the potassium aluminate from the resultingpressure; substantially as described.

5. The method of recovering the alkali-insoluble alumina contained inalunite inan alkali-soluble form, which comprises treating the aluniteat temperatures not exceeding 1400 C. with an oxid of an alkaline earth,and treating the resulting mass 'with a solution of an alkali in amountsufficient to combine with the excess of alumina, z. 6., that .part ofthe alumina which does not combine with the potassium oxid from thepotassium sulfate in the alunite; substantially as described.

6. The method of recovering the alumina contained in alunite in awater-soluble form,

which comprises treating the alunite at temperature not exceeding 1400C. with an oxid of an alkaline earth and with a suflicient quantity ofalkali to combine with the excess of alumina, e. that part of thealumina which does not combine with the potassium oxid from thepotassium sulfate in the alunite and dissolving out the watersolublealuminum compounds from the calcine; substantially as described.

7. The method of making the silicon compounds contained in raw aluniteinsoluble in water or alkali, which comprises treating the raw aluniteat temperatures not exceeding 1400 C. with an oxid of an alkaline earth;substantiallyas described.

8. The method of producing potassium sulfate from alunite, whichcomprises treating the raw alunite at temperatures not exceeding 1400 C.with an oxid of an alkaline earth together with an alkali sulfate;substantially as described.

In testimony whereof I affix my signature, in presence of two witnesses.

PAUL R. HERSHMAN. Witnesses:

OSCAR LAAGE, Jr., K. MA'NEY.

